What is the relationship between Perchlorate + porous silicon + crystalline water? 2

[LUFER]

Hello......I left an excerpt from the article and the points that I didn't really understand about it are in bold.

1. I didn't understand about this crystal clear water. I was able to research is that there are actually some crystals in the part of the molecules of the water itself, but I don't know exactly how it is really explicit in the same subject of the article.

2. I understood that certain perchlorates have this crystallized and hygroscopic water this can be a disadvantage in the long run, but I did not understand why it is still necessary to have this crystalline water to stabilize the pores of the silicon pores.


Highly explosive nanosilicon-based composite materials -

https://www.researchgate.net/public...plosive_nanosilicon-based_composite_materials

Due to packaging and long-term stability reasons only solid oxidizers incorporated into the pores of PSi have been explored. The most efficient oxidizers are perchlorates, since they have high oxygen content and are relatively stable in comparison to other oxidizers, e.g. chlorates. Therefore, we have chosen perchlorates as first choice for oxidizer. Unfortunately, most of the perchlorates contain crystal water and are hygroscopic (see Table 2). Non-hygroscopic perchlorates are KClO4 and RbClO4 but they are not solvable in common solvents. We found that perchlorates are much more efficient for explosive interaction than the analogue nitrates. We didn’t find any other oxidizer comparable with perchlorates but, because the energy yield of the reaction is very high, less efficient oxidizers can be sufficient for the possible industrial applications. On one hand, crystal water and hygroscopic nature of perchlorates are certainly disadvantages because they cause problems with long term stability of the samples. On the other hand, according to our experience it seems that at least the crystal water is necessary for stabilizing the salt inside of the pores. For instance, NH4ClO4 is not hygroscopic and contains no crystal water but after evaporation of the solvent it also creeps away of the pores. exactly how it is really explicit in the same subject of the article.

 

[Compositepro]

I'm not sure I understand what your questions are. It seems you do not really understand what "crystal water" is in the context of this article. Many salts form hydrates where the salt crystals contain water molecules as part of the crystal lattice structure. This kind of water can be removed by heating but that destroys the salt crystal.

 

[georgeverghese]

The article says many of the perchlorates have water of crystallisation and are hygroscopic, so not a good candidate as oxidiser for ignition reactions. KClO4 has no water of crystallisation but is not soluble in organic solvents. Best candidates are stated to be NaClO4 ( non hygroscopic and has only one molecule of water per molecule of perchlorate ( ie NaClO4.H2O) and sulfur( completely non hygroscopic).

 

[LUFER]

Thank you, as I do not know in depth the subject of the process, according to what I understand, the perchlorates have water crystallization, in the oxidation process, it interferes. Failing to find a reason, why can't attack the material.

I know that in the porous silicon manufacturing process, the electrolyte process is used, using 2 or 3 electrodes, a power source, in short a liquid such as hydrofluoric acid is placed where the silicon material becomes porous.

This point I was unable to understand about: Perchlorate is deposited in the porous silicon in the holes, because this crystallization process occurs, if depositing it is not as efficient because of the crystals and the less the crystals the better the result, right? The idea when smaller, the answer will be better, but in any case, there are these crystals, without them there is no ignition / explosion?